Vehicles typically include suspension systems. The suspension system of a vehicle is coupled to the vehicle frame and to each wheel assembly. The suspension system absorbs and dampens shocks and vibrations from the wheel assemblies to the vehicle frame. For each wheel assembly, the suspension system may include an upper control arm, a lower control arm, a coil spring, and a shock absorber. The shock absorber extends through the coil springs. One end of the shock absorber and the coil spring may be connected to the lower control arm, and the other end of the shock absorber and the coil spring may be connected to the upper control arm or to the vehicle frame.
The suspension system is arranged so that an upward motion of the wheel assembly, such as when the tire hits a bump while the vehicle is in motion, compresses the coil spring and the shock absorber. The coil spring may exert a force that is a function, e.g., a linear relation, of a difference between the current length of the coil spring and a relaxed length of the coil spring. The shock absorber may exert a force that is a function of a speed of compression or extension of the shock absorber.